Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$80.46	5.443%	$84.8394	$84.84	$84.85	$84.80
Purchase #2	$29.26	8.314%	$31.6927	$31.69	$31.70	$31.70
Purchase #3	$49.77	10.127%	$54.8102	$54.81	$54.80	$54.80
Purchase #4	$31.68	10.178%	$34.9044	$34.90	$34.90	$34.90
Purchase #5	$80.45	13.689%	$91.4628	$91.46	$91.45	$91.50
Purchase #6	$10.71	7.156%	$11.4764	$11.48	$11.50	$11.50
Purchase #7	$20.98	4.362%	$21.8951	$21.90	$21.90	$21.90
7 purchase totals =	$303.31		$331.0810	$331.08	$331.10	$331.10